Abstract: Geochemistry of pore water of marine sediments playes an important role in gas hydrate research. In order to detect the gas hydrater-bearing layers, geochemical characteristics and their implications for buried gas hydrates are studied with pore water collected from the Site GMGS2-09 in the southeastern part of the Pearl River Mouth Basin. Cations, anions, hydrogen and oxygen isotopic compositions are analyzed and studied upon previous researches. Chloride anomalies coupled with increased δ¹⁸O in pore water are observed at the depths of 9~17 meter, in which gas hydrate is recovered, 47 meter and 100 meter, which may indicate the presences of gas hydrate-bearing layers. Besides, gas hydrate saturation calculated indicates that it is 50% in depth of 17 m, and about 20% in depth of 47 m and 100 m.